The field of this invention relates to heterotrophic organisms and a process for culturing them for the production of lipids with high concentrations of omega-3 highly unsaturated fatty acids (HUFA) suitable for human and animal consumption as food additives or for use in pharmaceutical and industrial products.
Omega-3 highly unsaturated fatty acids (HUFAs) are of significant commercial interest in that they have been recently recognized as important dietary compounds for preventing arteriosclerosis and coronary heart disease, for alleviating inflammatory conditions and for retarding the growth of tumor cells. These beneficial effects are a result both of omega-3 HUFAs causing competitive inhibition of compounds produced from omega-6 fatty acids, and from beneficial compounds produced directly from the omega-3 HUFAs themselves (Simopoulos et al., 1986). Omega-6 fatty acids are the predominant HUFAs found in plants and animals. Currently, a commercially available dietary source of omega-3 HUFAs is from certain fish oils which can contain up to 20-30% of these fatty acids. The beneficial effects of these fatty acids can be obtained by eating fish several times a week or by daily intake of concentrated fish oil. Consequently large quantities of fish oil are processed and encapsulated each year for sale as a dietary supplement. However, there are several significant problems with these fish oil supplements, including bioaccumulation of fat-soluble vitamins and high levels of saturated and omega-6 fatty acids, both of which can have deleterious health effects.
Another source of omega-3 HUFAS is the microflora Thraustochytrium and Schizochytrium which are discussed in detail in related U.S. Pat. No. 5,130,242. These microflora have the advantages of being heterotrophic and capable of high levels of omega-3 HUFA production. There still exists a need however for improved methods for fermentation of these microflora and identification of improved uses of the microflora product.
The present invention is directed to a new process for growing the microflora Thraustochytrium, Schizochytrium, and mixtures thereof, which includes the growing of the microflora in a culture medium containing non-chloride containing sodium salts, particularly including sodium sulfate. More particularly, a significant portion of the sodium requirements of the fermentation are supplied as a non-chloride containing sodium salt. The present process is particularly useful in commercial production because the chloride content in the medium can be significantly reduced, thereby avoiding the corrosive effects of chloride on fermentation equipment. In addition, the present invention is particularly useful for production of food products for use in aquaculture because Thraustochytrium and Schizochytrium cultured in such media form much smaller clumps than those cultured in high chloride media and are thus more available as a food source for larval shrimp. In particular, Thraustochytrium and Schizochytrium cultured in medium containing sodium sulfate can have cell aggregates of an average size of less than about 150 microns in diameter.
A further embodiment of the present invention is the production of a microflora biomass comprising Thraustochytrium, Schizochytrium, and mixtures thereof which have an average cell aggregate size of less than about 150 microns. The microflora biomass is useful for aquaculture and in particular, for feeding larval shrimp because the microflora have the primary feed advantages required for shrimp of a high sterol content and a high omega-3 highly unsaturated fatty acid (HUFA) content. Additionally, because of the small cell aggregate size, the microflora can be eaten by the larval shrimp, brine shrimp, rotifers, and mollusks. The present invention further includes a process for the production of these organisms which includes feeding Thraustochytrium, Schizochytrium, and mixtures thereof, having an average cell size of less than about 150 microns to them.
A further embodiment of the present invention is directed to a food product which is comprised of microflora selected from the group consisting of Thraustochytrium, Schizochytrium, and mixtures thereof and an additional component selected from the group consisting of flaxseed, rapeseed, soybean, avocado meal, and mixtures thereof. A particular advantage of this food product is that it has a high long chain omega-3 fatty acid content and a high short chain omega-3 fatty chain content from the additional component. In a further embodiment, the food product is produced by extrusion. The extrusion process involves mixing the microflora with the additional component, thereby reducing the moisture content of the food product. The food product is then extruded under heat, thus driving off a significant portion of the reduced moisture. The remaining amount of the original moisture content is readily removed by air drying or short baking times, thereby reducing the overall energy requirements of drying and the potential degradation of the omega-3 HUFA""s by extended drying at high temperatures.